Finned projectile support and guide



March 13, 1962 H. R. SMITH FINNED PROJECTILE SUPPORT AND GUIDE FiledAug. 18, 1961 INVENTOR. HERBERT R. SMITH ATTORNEY States Unite Theinvention described herein may be manufactured and used by or for theGovernment for governmental purposes without the payment to me of anyroyalty thereon.

The invention relates to a support and guide for finned projectiles ordecoys to be simultaneously ejected from opposite sides of a missile. Anobject of this invention is to provide such a support and guide which isof much less weight than is the projectile and which is capable of beingattached to a launching tube in a cone of a missile where there is onlyabout an inch clearance between a side of the missile when saidprojectile is placed between an end of said launching tube and the sidewall of the missile. Another object is to provide such a support andguide that does not have to extend around the outside of the finnedprojectile but may engage the side walls of the fins in guiding.

The finned projectile, its size, weight, and shape were designed fordecoy purposes and launching from opposite sides of a missile duringflight without having recoil change the missile from its intended pathand target, before the present invention. With foregoing clearance andweight limitations the problem of obtaining a suitable support and guideseemed extremely diflicult if not hopeless. Nevertheless the task wasundertaken.

According to this invention the supporting function was found possiblewith only a short aluminum adapter longitudinally over-lying part of theexisting launching tube and part of the projectile. In combination withsuch an adapter fixed to a launching tube, a longitudinally slottedguide tube was found to be capable of the desired guiding function whensharing some of the aforementioned supporting function and when theguiding was transferred from the peripheral edges of the fins to theside faces of these fins. In addition a spring, an abutment disc, andretainer ring were found desirable to assist in supporting theprojectile without objectionable looseness before being fired or ejectedand the provision of such discs of slightly different diameters wasfound to be a way of increasing the build up of propellant pressurebefore the launching of the projectile occurred so that velocity ofthese projectiles could be controlled readily without elaborrate weightand space consuming additional elements.

Referring to the drawings:

FIG. 1 is a diagrammatic representation of the opposed launching tubesin the cone of a missile;

FIG. 2 shows the adapter and guide tube around a projectile;

FIG. 3 is an enlarged detail showing the guide tube within the adapterbut without the projectile or decoy being shown.

In FIG. 1 is shown the opposed launching tubes 10 and 11 of the priorart to this invention fixedly located in the cone 12 of a missile.Between the tubes 10 and 11 is propellant chamber 13 for moving pistonsoutwardly in the launching tubes for ejecting projectiles one of whichis shown in FIG. 2. The usual propellant is fired by an electric primerthrough the wires 14. Two launching tubes are oppositely arranged tofire two decoy finned projectiles laterally so that when the projectilesare of equal size and weight the missile will not be moved from itsplanned path or target by equal and opposite recoil thrusts. FIG. 2shows one launching tube 11 having aent "ice

therein a usual piston 15 and piston rod 16. Each launching tube isthreaded into the propellant chamber 13.

To support and guide the decoy projectile having fins 20 as it isejected by the piston rod 16, an adapter 18 is threaded onto the outsideof tube 11 and is of aluminum for the purpose of keeping the supportingand guiding attachments as light in weight as possible. Within theadapter 18 is an enlarged end 17 of the piston rod 16 which ishereinafter referred to as a plunger. As may be seen from FIGS. 2 and 3an aluminum guide tube 19 is in threaded engagement within the adapter18 for providing an auxiliary support and guide for the decoy projectilehaving fins 20. A principal guiding is achieved by the cooperation ofthe edge faces of the slots 21 with the side faces of the fins 20. Inthe embodiment illustrated there are four fins on the projectile. Thereare also four slots 21 in the guide tube the side walls of which do animportant part of the projectile guiding as it is being ejected bypropellant pressure acting on the piston 15, piston rod 16 and plunger17.

FIGS. 2 and 3 show how the adapter 11$ is also provided with short slots23 in prolongation of the slots 21 in the guide tube 19. In fact noassist in guiding the projectile or decoy by its fins, the long slots inthe guide tube are in prolongation of the short slots 23 in the adapter18 for receiving the rear end portion of fins 20.

A spring 24 of helical shape is shown in FIG. 2 in cooperation with theplunger and projectile to prevent looseness of the projectile in itsholder or combination of adapter 18 and guide tube 19. A stifi but thinplastic washer (not shown) is placed between the right end of spring 24in FIG. 2 and the projectile to distribute the pressure applied by theend of spring 24. A pair of small holes 25 on opposite sides of thepiston rod are provided in the partition wall of the adapter to avoidthe formation of a gas cushion acting on the piston to slow down itsejection movement and prevent the projectile having as strong an outwardmovement as desired. On the outside of guide tube 19 is a retainer ring26 having extensions 27 into the slots 21 and extending forwardly of theprojectile. These extensions 27 serve as abutments for the disc 28 alongthe forward end of the projectile as shown in FIG. 2. Increasing thediameter of the stiff steel abutment disc 28 has the effect of movingthe outer portions 22 of the guide tube 19 which are at the front end ofguide tube, radially outward a slight amount providing a taper on outerends which slope rearwardly when the disc is larger in diameter. Bycausing a greater stress to be placed in the ring 26 the build uppressure of propellant needed to eject the projectile may be increasedto give the projectile a higher velocity. This increased tension in ring26 is obtainable in several ways. The ring may be wider (longitudinallyof the projectile) to cause engagement of the ring by the fins beforethe front end of the projectile contacts disc 28 and thus move the ringup the incline under pressure placing the desired tension in ring 26,before the front end of the projectile contacts disc 28 and moves it outof the way. Another way of increasing projectile velocity is to increasethe thickness of disc 28 alone giving it less resiliency and preferablywith a sharper peripheral edge which will cut into the softer aluminumguide tube and make an abutment requiring greater propellant pressure topush the disc 28 out of tube 19. Either or both of these means may beused. The forward end of the projectile usually moves disc 28 out of thetube. Where greater pressure build up is desired the disc 28 is placedfar enough in front of the forward end of the projectile to allow themotion of the projectile to push the retainer ring up its incline forobtaining this larger pressure build up. This ring may rupture intension before the extensions 27 contact the disc 28 or else the upwardmovement of disc 26 may be no more than enough to obtain the desiredpressure when the extensions 27 push the disc 28 before the projectiledoes. A wider retainer ring enables this ring to be moved by the finspushing it up any incline created by a larger diameter disc 28 forrequiring the desired propellant pressure before the ring 26 ruptures orbefore the disc 28 is pushed out of place. Extensions 27 may not beprovided on the ring 26 but may be used when desired. When disc 28 ispushed by the projectile, its rounded front end will engage the centerof disc 28. Application of stress to the center of this disc will tendto flex it more than a stress applied by extensions 27 to an outer edgeportion of the same disc, depending of course upon its thickness.

Among the advantages of this invention may be mentioned the absence ofany larger diameter outside guide for the projectile fins. Instead theprojectile is guided on ejection by the side faces of the fins engagingthe side walls of the slots in both the adapter and guide tube. Thecombined weight of the plunger 17, adapter 18, spring 24, guide tube 19,retainer ring 26 and disc 28 is between about one third and one fourththe Weight of the finned decoy projectile. The additional space requiredfor the support and guide functions for the projectile is but a smallminor fraction of the projectile length beyond the front end oflaunching tube or about one inch. This distance is shown in FIG. 2 asbeing from the rear end of the fins backward to the front end of thelaunching tube 11. Simple means are thus provided whereby the velocityof the decoy projectile may be increased or decreased.

I claim:

1 In a missile cone having opposed pressure launching cylinders withpistons and piston rods for simultaneous ejection of finned projectilesin opposite directions laterally from a missile, the combinationtherewith of the improvement for retaining a projectile fixed withrespect to its launching cylinder prior to its ejection and for guidinga finned projectile on launching, said improvement being also of lessdiameter than that of the fins, of lighter weight than said projectile,not much longer than said projectile, and comprising an adapter tubesecured over an end of a launching cylinder, a longitudinally slottedguide tube secured to said adapter, the slots in said guide tubeextending over a major portion of its length and in alignment with slotsin said adapter extending for but a minor part of the length of theadapter, the slots in said guide tube and adapter being of a Width toreceive and guide the projectile fins, a helical spring within saidadapter for cooperation with a rear end of said projectile and with anend portion of said piston rod, a retainer ring slidable on an outer endportion of said guide tube, and an abutment disc for insertion in thefront end of said guide tube contiguous said projectile, of a hardermaterial than said guide tube, the diameter of said disc being adaptedto expand the fore end of said guide tube, whereby the diameter of saidabutment disc and position of said retainer ring in clamping said discwill determine the degree of pressure build up in the launching cylinderfor ejection of said projectile.

2. An apparatus according to claim 1 in which the front end of saidpiston rod is provided with an enlargement against which said helicalspring may press, and said retainer ring being provided on its rear edgewith extensions entering the slots in said guide tube and projectingforwardly into contact with said disc.

3. The combination with an adapter tube for attachment over a front endof a pressure launching tube for a finned projectile when said adapterand launching tube are of less diameter than said projectile fins, aguide tube for a finned projectile forthreaded attachment to saidadapter and longitudinally slotted through which projectile fins mayextend and .be guided by the side edges of the guide tube slots onejection of such a projectile, a retainer ring slidable over said guidetube front end portion, and an abutment disc of a size to expand thefore end of said slotted guide tube, whereby said ring may clamp thedisc in said guide tube by pressure of said guide tube fore end upon theedge of said disc.

No references cited.

